Hi Roy -
On Wed, 25 Apr 2007, Roy Williams wrote:
> Doug, Kona, Pedro
>
> It seems to me that the TAP consists of these parts:
> (a) There is a Query
> (b) that is wrapped in the Protocol and sent to the service
> (c) that may be Managed synchronous or asynchronous
>
> And it seems to me that
> (a) Query is about ADQL, mostly handled by the VOQL group
> (b) Protocol is about TAP, mostly for the DAL group
> (c) Management is about GET/REST and UWS, mostly for the GWS group
Ok so far. (minor detail: query can be parameter-based as well as ADQL-based; but all agree VOQL WG is responsible for ADQL).
> When the query (a) is a getCapabilities query, the most interesting return is
> (1) the tables and attributes (SQL metadata) rather than
> (2) the VOResource registry entry.
This is correct, *except* that what you wrote should read as follows:
> When the query (a) is a [table metadata] query, the most interesting
This ability to query table metadata, e.g., the list of tables and their properties, and the columns of an individual table, is an important feature of TAP, and is required to be able to query arbitrary data tables.
getCapabilities on the other hand, is a separate service operation, used to return the service metadata, describing the capabilities of the service. Any client can use this information, but one very important one is the Registry, which will cache this information in a VOResource, so that clients can search for services based on their capabilities.
> This data dictionary (1) can come back the same way as any other table -- a
> VOTable or CSV etc.
Yes indeed.